I think I remember hearing about our trucks being offered with a factory OD tranny. Is this true, or have I lost my mind?

Edit: I just checked my brochure, and there was an OD offered.

So my next question is, how would I identify one?

 

I believe the OD's were top loaders. Light duty, probably only offered w/ 300 six or 302. Shift linkage would have been on the side of the case. When in fourth gear, count output shaft rotation. Output will spin slightly more than one rotation for each rotation of the input shaft.

 

Thats hard to do if it is mated to the engine. Is there a casting number or some kind of visual identifier to distinguish them?

 

yes there was the top loader behind the 302. it was a car tranny put in a truck. it did not hold up well at all and was a bad tranny for a truck.

 

Can it be rebuilt stronger?

 

the late-70s Clark OD is really a strong trans with a bad reputation (most often confused with the 80's Mazda OD transmission).

It will have a LONG cast Iron slip yoke style tailshaft and look like a toploader with a bulge on the passenger side of the main case.

No creeper gear, 4 sycro-ed gears , a 3.03 1st gear, .85 OD. Look for case #s:
RUG BP
RUG CA
RUG CL
RUG CD
chrome hurst shifter with a ford part #, 1-1/16" 10 spline input shaft

shift pattern is:
R13
..2OD

78-79 F150s
78-81 E100/150 vans (the van shifter mount bracket is slightly different than the truck shifter bracket)

 

Thats what I was looking for!!!! Thanks!!!

 

It looks like it was offered with the 351M in the F250s

That means it will fit behind a 460

 

Ford Motor Company published a TSB for this 4-Speed Overdrive Transmission in Sept. '81 for main bearing failure. The way Ford made the old top-loader into an overdrive transmission was through the use of a fancy shift linkage. When the shift lever is placed in the "third" gear position, the top-loader is actually shifted into its "fourth" gear position, with power flowing flowing through the mainshaft, as in "direct" drive, with a 1:1 ratio. When the shift lever is moved to the OD position, the top-loader is actually shifted into its "third" gear position, with power flowing through the countershaft, and the countershaft gears provide the OD ratio.

The main bearings absorb higher forces in an overdrive transmission than in a non-overdrive transmission, and becasue they spend so much time with the mains loaded in "top' gear, the mains take alot of punishment. (This is why the owners manual states that you are not suposed to tow anything with a vehicle equiped with this transmission.)

The TSB specifies a specific bear that is to be used as a replacement bearing to stand up to this abuse. The bearings are Ford Part Number D8OZ-7025-A and are identified on the bearing as KOYO No. 83763-1.

I had to replace the mains in my '79 F-150 with this transmission at about 80k miles. Using these replacement bearings, I now have 223k miles on the transmission and tow about 600 miles a year.

BTW, this transmission has relatively wide ratios (3.29, 1.84, 1.00, 0.79) with significant RPM drops in the lower gears (1st/2nd = 44%, 2nd/3rd = 46%, and 3rd/OD = 21%. Be sure and use a cam that has good torque in the lower RPM range.

When I ordered the truck the only rear end ratio they were installing with this tranny was the 2.75 9-inch, which was about 1500 RPM @ 60 mph with the factory L78 tires - just too much for the little 302 if there was a head wind.

When I rebuilt the Traction-Lok, I installed 3.25 rears, which with the current 235/70-15s yields about 2000 RPM @ 60 MPH. This is a much better combination with the OD tranny for the type of driving I do, and I gained about 1 mpg on the two lane roads, while losing about .5 mpg on the Interstate highways.

Just in the way of a FYI, I had an awful time finding the correct speedometer gear for this set up, as this transmission has a "right-hand twist" speedometer gear and the Ford Dealers only listed the 17-tooth gear, while I needed a 19-tooth gear. Someone on this list steered me in the right direction as the gear I needed was from an early 60's big Ford, IIRC.

 

Thanks pdqford! More good info.